The relationship between income and performance indicators in general practice: a cross-sectional study.

Objective: To explore the relationship between the income of general practitioners (GPs) and the performance characteristics of their practices.

Design: Cross-sectional survey.

Setting: All practices (n = 166) in an inner city health authority, two years before the introduction of the new GP contract in April 2004 were studied.

Main Outcome Measures: True income per GP was unavailable to us. Instead, the proxy measure - superannuable pay - was calculated (gross eligible income per GP minus the national average sum for GP expenses). Practice staff funding figures were also obtained. These two financial indicators were compared with practice characteristics and performance indicators.

Results: Data were available from 151 out of 166 practices. Based on regression analysis, larger list sizes and higher practice staff budgets predicted 31% of the variation in GP income (standardized beta = 0.66, P < 0.001; beta = 0.19, P = 0.02; respectively). Higher staff budgets were independently associated with better cervical smear and two-year-old vaccination rates (standardized beta = 0.24, P < 0.01; beta = 0.18, P = 0.03; respectively). No association was demonstrated between performance indicators and income.

Conclusion: Under the previous contract, GPs were able to maximize their income by taking on more patients, whereas achievement of performance targets had very little impact on overall income. The opportunity costs of pursuing higher-quality care might have outweighed the modest financial rewards attached to performance targets. Provided rewards for good-quality care are sufficiently high, the new GP contract is likely to tip the balance in favour of generating earnings by improving the quality of clinical care. To deliver this care, as measured by available performance indicators, our findings imply that a greater investment in practice staff will be needed.